Creating 'Schrödinger's virus' in the lab

In 1935 Erwin Schrödinger devised his famous thought experiment – in which a cat is both alive and dead at the same time – to highlight the paradoxical nature of quantum mechanics. Now, a group of physicists in Germany and Spain believe that it should be possible to build an experiment in which an actual living creature such as a virus is held in a superposition of quantum states.

Schrödinger imagined a cat being held in an opaque box that also contained a glass vial of cyanide. Next to the vial there were a radioactive source, a Geiger counter and a hammer, set up so that decay would lead to the smashing of the vial and the poisoning of the cat. However, the radioactive source would be so weak that within an hour, say, there would only be a 50:50 chance that decay could take place. Before an observer opens the box and looks inside, quantum mechanics tells us that the radioactive material would be in a quantum superposition of both having experienced a decay and not, and that the cat would therefore also exist in a quantum superposition – of being simultaneously alive and dead.

Schrödinger's scenario illustrates the seeming irreconcilability between the indeterminate quantum realm and our everyday world of concrete – and living – objects. However, physicists have started to probe the boundary between the quantum and the classical and are finding that relatively large objects can be held in superposition states. Such objects include molecules like fullerene carbon-70, as well as hoops of superconducting material that contain currents circulating in opposite directions at the same time.

Superposition of living creatures?

Now, researchers hope to observe superpositions of even larger "optomechanical" systems – objects, such as tiny mirrors or cantilevers, which respond mechanically when exposed to laser light. It is one such system that Oriol Romero-Isart of the Max Planck Institute for Quantum Optics in Garching and colleagues say could be used to demonstrate the superposition of living creatures.

Their plan is to trap an organism inside an optical cavity using "optical tweezers" – a laser beam tightly focused on a tiny region in space that can confine objects in three dimensions. The radiation pressure of a second laser would then slow down the organism's centre-of-mass motion so that it exists in its motional ground state. Finally, a single-photon pulse from the second laser would put the organism into a superposition of its ground state and an excited motional state.

The German-Spanish group points out that an organism must satisfy three basic requirements if it is to be placed in a superposition in this way. First, they say, it must approximate a dielectric object so that it is very transparent but still refracts light. This means that when the organism moves, the properties of the optical cavity change, varying the light intensity inside the cavity and therefore the force on the organism, which is what cools it. Second, the organism must be smaller than the wavelength of light used, about 500 nm, so that it can be confined between the peaks and troughs in the light wave. Finally, the organism must be able to withstand extremely low pressures, because the merest trace of air molecules would rapidly lead to the decoherence of its quantum states.

Common flu a candidate

The researchers say that the common influenza virus would be a good candidate for the experiment because it is about 100 nm long and can exist in a vacuum. Alternatively they might use the Tobacco Mosaic Virus, which is 50 nm wide and can also withstand very low pressures. Both viruses are good approximations of dielectric objects.

Romero-Isart and colleagues believe that studying organisms in this way could have profound implications. "We expect these proposed experiments to be a first step to experimentally address fundamental questions," they write in their paper, "such as the role of consciousness in quantum mechanics, and to make distinctive many-world and Copenhagen interpretations."

Good news for cats

Maciej Lewenstein of the Institute of Photonic Sciences in Barcelona believes that the experiment is feasible using existing technology and agrees that it could have exciting implications. "Proving that quantum-mechanical phenomena exist at this large scale would open the road to studying the role of quantum mechanics in biology," he says. However, he cautions that it may be some time before we can understand the relationship between consciousness and quantum mechanics. He also doubts that it will ever be possible to carry out Schrödinger's experiment as applied to actual cats, which, he adds, "is probably good news for cats".

If he were still around, he'd be pretty upset to see his cat being generally used in support of the Copenhagen Interpretation. But that's interpretation for you. It has a habit of airbrushing over history, it's very difficult to distinguish experimentally, and it can stray a long way from the underlying physics. For example, the uncertainty principle says this:

"In quantum mechanics, a particle is described by a wave. The position is where the wave is concentrated and the momentum is determined by the wavelength. The position is uncertain to the degree that the wave is spread out, and the momentum is uncertain to the degree that the wavelength is ill-defined."

This meaning here is crystal clear when one reads what it says, and considers long-wave radio: a photon is an extended entity, and is a wave rather than a billiard ball point particle. Thence even if "configured" as a vorton via say pair production, it remains an extended entity and a wave, hence superposition applies, regardless of consciousness or many-worlds.

Living Matter & Decoherence

My simple question is what constitutes `living' for a virus ?If it is trapped in a vacuum, how does one ascertain whether it is alive or dead ? In other words, is it not just a huge biomolecule ?It would seem that if this experiment can be successfully carried out, this is hardly proof that conventional living systems, e.g., bacteria, can be put into a cat state, since they typically require temperatures near 300k, and can reproduce on their own. Viruses cannot, & require a bacterium for a host. Moreover, decoherence times at 300k are too brief to support a stable cat state long enough to be observed.Thus it would seem that a bare virus would not constitute a conventional living system.

Shrodinger life form

Buy lucky dip ticket for the UK lottery. This will be generatedelectonically. Don't look at it. When the draw is made don't look at the results. Until you check the outcome (do so within 6 months) you will be in the quantum superimposed state of millionaire / non millionaire.

The Schrodinger's quantum cat experiment is a two-state system with a two-dimensional state vector. Quantum mechanics gives us only two bits of information:

1. When we observe the cat, we find it either dead or we find it alive. These are the only possible results. The orthonormality of the eigenvectors prevents us from finding the cat both alive and dead at the same time.2. From the state vector, we calculate the probability of obtaining each result.

A quantum experiment requires an experimental result, and any speculation about the behavior of the cat prior to measurement cannot be verified: the pre-measurement experiment is not defined in quantum mechanics.

If the virus experiment is successful, then the virus will be found in either its ground state or in an excited state. It will never be found in its ground state and in an excited state at the same time. Repeating the experiment many times will give the probability distribution of those results. All of which is predicted by quantum mechanics.

Particle duality and living organisms

I disagree that a photon is just an extended particle. It has duality, and how that duality manifests itself depends on the nature of how you detect it. If it was just a wave, many developments that depend on the particle interpretation, such as solar cells, would not operate. Remember, the wave interpretation relates to the probability of 'finding' a particle at coordinates (x,t).

With higher lifeforms, such as a feline, there is "experimenter effect", I would think. The creature would "observe", thereby changing the outcome of the experiment. Because in the box, the cat is within the experimental system and can affect it's outcome. As an example, the cat may swat the vial, knocking it over, biasing the experiment towards a live cat vs. a dead one.Though Schrödinger's gedanken experiment beautifully illustrated one of the counterintuitive characteristics of quantum mechanics, I don't believe it would work in practice because of the "observer" aspects of living beings in general.

While there's merit in the basis of this kind of thought experiment, it seems to me this particular kind was the result of 19th century-minded people being quite concerned over the argument of free will - as uncertainty ultimately implies - to which my advice is to let it go, kids.

If he were still around, he'd be pretty upset to see his cat being generally used in support of the Copenhagen Interpretation. But that's interpretation for you. It has a habit of airbrushing over history, it's very difficult to distinguish experimentally, and it can stray a long way from the underlying physics. For example, the uncertainty principle says this:

"In quantum mechanics, a particle is described by a wave. The position is where the wave is concentrated and the momentum is determined by the wavelength. The position is uncertain to the degree that the wave is spread out, and the momentum is uncertain to the degree that the wavelength is ill-defined."

This meaning here is crystal clear when one reads what it says, and considers long-wave radio: a photon is an extended entity, and is a wave rather than a billiard ball point particle. Thence even if "configured" as a vorton via say pair production, it remains an extended entity and a wave, hence superposition applies, regardless of consciousness or many-worlds.

The wikipedia article is written by laymen, and is fundamentally incorrect as to the standard formulation of QM, as taught in any graduate physics course. The photon is not spread out, and this has been conclusively proven by actual experiments, e.g. see Quantum Mechanics, A modern Development Leslie Ballentine. QM describes particles, and allows for calculating what the probability of finding such a discrete particle is, in a given volume of space. Only the most likely position of the particle is typically given by the center of the wave function. Indeed, the wave function may not be even symmetrical, so that its average position may not even be the median position.

If he were still around, he'd be pretty upset to see his cat being generally used in support of the Copenhagen Interpretation. But that's interpretation for you. It has a habit of airbrushing over history, it's very difficult to distinguish experimentally, and it can stray a long way from the underlying physics. For example, the uncertainty principle says this:

"In quantum mechanics, a particle is described by a wave. The position is where the wave is concentrated and the momentum is determined by the wavelength. The position is uncertain to the degree that the wave is spread out, and the momentum is uncertain to the degree that the wavelength is ill-defined."

This meaning here is crystal clear when one reads what it says, and considers long-wave radio: a photon is an extended entity, and is a wave rather than a billiard ball point particle. Thence even if "configured" as a vorton via say pair production, it remains an extended entity and a wave, hence superposition applies, regardless of consciousness or many-worlds.

The wikipedia article is written by laymen, and is fundamentally incorrect as to the standard formulation of QM, as taught in any graduate physics course. The photon is not spread out, and this has been conclusively proven by actual experiments, e.g. see Quantum Mechanics, A modern Development Leslie Ballentine. QM describes particles, and allows for calculating what the probability of finding such a discrete particle is, in a given volume of space. Only the most likely position of the particle is typically given by the center of the wave function. Indeed, the wave function may not be even symmetrical, so that its average position may not even be the median position.

Buy lucky dip ticket for the UK lottery. This will be generatedelectonically. Don't look at it. When the draw is made don't look at the results. Until you check the outcome (do so within 6 months) you will be in the quantum superimposed state of millionaire / non millionaire.

Technically yes, but not 50-50 in terms of probability (which is the case with the cat). The probability that you've won is very small!

Viruses are alive?

The superposition state is achieved, as far as we can tell, by its property of not being able to be observed by an “intelligence”. Once it can be measured, it is no longer in superposition. So the question that arises is; is that cat\virus intelligent enough to observe? That could also be the answer as to why we don’t find things in the macroscopic world in superposition, we are here to observe it.

One question I have is how are they going to be able to determine if the virus is in superposition? Won’t they have to observe it to tell?